Process for dyeing blends of nylon 6 and nylon 66



3,105,732 PROCESS FOR DYEING BLENDS F NYLON 6 AND NYLGN 66 Hans Ortheil,Rocky Mount, N.C., assignor to Burlington Industries, Inc, Greensboro,N.C., a corporation of Delaware No Drawing. Filed Jan. 10, 1961, Ser.No. 81,674

6 Claims. (Cl. 8-21) The present invention rel-ates to certainimprovements in the dyeing of nylon.

One of the principal objects of the invention is to provide a noveldyeing procedure for obtaining maximum shade contrast between twodifferent types of nylon fibers, namely the so-called nylon 6 and nylon66, when these fibers are dyed together. It is also an object of theinvention to provide a process for avoiding barr effect in the NH(CONH.( CH -COOH while nylon 6'6 may be illustrated as NH [CO NH-( CHCONH--(OH ,,COOH

n representing a Whole number in both instances.

If it were possible to segregate an individual molecule of each of thesetypes of nylon and dye these two molecules together, it is probable thatan identical dyeing effect could Other objects will also be here- .beobtained. However, as a practical matter, these nylons do not dye to thesame shade when dyed together presumably because of physical differenceswhich occur as a result of the procedures used in manufacturing same.The customary step of stretching these fibers so that the molecules areoriented and lay in bundles side by side and end to end on their longaxes, is believed to have a particular effect in physicallydifferentiating these two types of nylon. Thus, in the case of nylon 66,there is apparently a high geometric orientation, the passways betweenthe molecules are of a definite size and only dye particles equal to orsmaller than the size of these passways may penetrate the fiber.

V. N. Nikitin (J.S.D.C. 69,227) (1953) found by infrared spectrum thatdifferent maxima in the NH bond existed for nylon 6 than nylon 66.Ortheil (Dissertation 1955, Stgt.) found nylon 6 has differentelectrostatic areas due to preferable concentration of amino or carboxylgroups. This may indicate that nylon 6 is less subject to a geometricalorientation. Due to the volume of atoms and steric hindering (spaceblocking), more and some larger passways exist in nylon 6 than in nylon66.

As understood in the art, dyestuffs attach themselves to the nylonmolecule at the NH (amino) site at one end of the linear chain molecule,at the CONH (amide) site in the center of the chain, and at the COOH(carboxyl) site at the other end of the chain. In the latter case, thisis done only in an alkaline medium.

By virtue of the physical differences discussed above, it is possiblethat dye molecules which are very slightly larger than the passwaysbetween the molecules of nylon 66 will not get into the passways so thatthey can attach themselves to the amide group on the nylon molecule.However, this same molecule may enter the passageways between nylon 6molecules as these passways are larger than the nylon 66 passways, andthe molecule of dye may thus attach itself to the nylon 6 amide groups.Presum- States harem ice ably, this is why nylon 66 dyes more lightlythan nylon 6 when these two types of nylons are dyed together.

In any event, and despite the shade differences which can be obtainedwhen dyeing nylon 6 and nylon 66, there are times, eg for stylingpurposes, when it may be desirable to obtain a product comprising aneven greater shade contrast, i.e. where the nylon '66 fibers areessentially undyed with substantially full dyeing of the nylon 6 fibers.The present invention makes it possible to accomplish this result forthe first time in a straightforward and highly effective manner.

According to the present invention, it has been found that optimum shadecontrast can be obtained between nylon 6 and nylon 66 fibers by dyeing amixture of these fibers in an essentially neutral dyebath (pH betweenabout 6.5 and 7.5) which contains, in addition to the nylon dyestulf ordyestuffs, polyvinylpyrrolidone or the like and ethoxyl ated tallowalcohol or the equivalent thereof.

The exact reason for the success of the present invention is not fullyunderstood. However, it is believed that the unique results of theinvention are due to the following factors although it is not intendedthat the invention should be limited to this explanation:

(a) The neutral or slightly acid dyebath appears to prevent dyeing ofthe carboxyl (COOH) group at one end of the nylon molecules;

(b) The polyvinylpyrrolidone has a greater affinity for the nylondyestuif than either nylon 6 or nylon 66 and, in a sense, preferentiallyabsorbs the dyestuffs or forms a complex thereof thereby preventing thedye molecule from attaching to the amino (NI-l group of the nylons; and

(c) The ethoxylated tallow alcohol or the equivalent partially dispersesthe polyvinylpyrrolidone-dye complex and because of the large micellestructure which this dispersing agent builds into the solution, theresulting polyvinylpyrrolidone-dye-ethoxylated tallow alcohol system isconfined to a particle size which is larger than the passways betweenthe nylon 66 molecules but smaller than the passways between the nylon 6molecule so that the dye molecules can attach itself to the amide groupsof the nylon 6 but not those of the nylon 66.

While polyvinylpyrrolidone is preferred, it is possible to use in lieuthereof, or in addition thereto, some other water-soluble compound oflike characteristics which has a higher affinity for the dyestufi thanthe nylon and will form an equivalent complex therewith. Typicalalternatives are oxazolidiones such as polyvinyloxazolidione andhydantoin.

The amount of polyvinylpyrrolidone or the like utilized herein may varyconsiderably. The more of this agent that is used, the more slowly thedyebath will exhaust. Amounts ranging from 0.5% to 1% on the Weight ofthe fiber, using about a 20 to 1 water/fiber ratio, are generallysatisfactory. Preferred conditions would involve the use of essentiallyequal amounts of polyvinylpyrrolidone and dysestuff required to developthe shade.

Ethoxylated tallow alcohol is the preferred dispersing agent for useherein but other materials may also be used, e.g. partially sulfonatedlong chain saturated fatty acids, such as partially sulfonated stearic,lauric or palmitic acid or essentially similar dispersing agents whichbuild in solution a large micelle structure.

The amount of et-hoxylated tallow alcohol and/ or other dispersing agentused herein may be varied as desired. Usually, however, from 0.5% to 2%by weight of the fibers being dyed will give satisfactory results withabout 1% representing the preferred amount.

Any of the conventional dyestuffs for nylon can be used in the presentinvention. These are usually anionic dyestuffs land as suitable theremay be mentioned the following representative groups: acetate dyes, aciddyes and unetallized dyes. Typical specific examples of such dyestuffsare:

HzN

wherein Me stands for Cu, Co, etc., and R is :an organic radical, e.g.methyl or other alkyl.

The nylon 6 and nylon 66 fibers as dyed herein may be in either fabricor non-fabric form. The fabric or other mixture of these fibers mayinclude additional fibers such as cellulosics, wool, Dacron, Orlonand/or other natural or synthetic textile materials. These other fibers,e.g. cellulosic, may be dyed with direct dyes while simultaneouslydyeing the nylon. Due to the retarding action of thepolyvinylpyrrolidione or the equivalent on the ability of direct dyes tostain nylon, it is not necessary to incorporate in the bath a direct dyeinhibitor for nylon such as an alkyl naphthalene sulfonate.

The dyebath of the invention may include conventional amounts of thenylon dyestuff or dyestuffs. Usually, this will amount to from 0.5 to6.0% by weight of the fibers being dyed. Generally, the dyebath water tofibers ratio is such as to provide from 12 to 40 parts water, preferablyparts, per part fibers, on a weight basis.

The dyeing time and temperature may be widely varied. Usually, however,satisfactory dyeings can be obtained by operating at 180 to 200 F. forfrom 60 to 300 minutes at atmospheric pressure. Slight variations inpressure may be used as desired.

The invention is illustrated, but not limited, by the following exampleswherein parts and percentages are by weight unless otherwise indicated:

Example I Woven fabric consisting of 107% nylon 6; 10.7% nylon 66; 15.6%viscose rayon and 63% cotton was scoured thoroughly in 1a dyebeck inconventional manner using an alkaline scour with a non-ionic detergent(i.e. Triton X400) until all size and oil were removed. The thus scouredcloth was then well rinsed in water.

Water was then fed into the dyebeck in an amount sufficient to give a20:1 ratio by weight of water to fabric. The water was heated to 100 F.and there was then added 1% of the weight of the cloth of ethoxylatedtallow alcohol (previously dispersed in water). The cloth was then runin the beck for 10 minutes at 100 F.

Thereafter 1% of polyvinylpyrrolidone (previously dissolved in water)was added to the dyebeck followed by 4% of previously dissolved directdyestuffs (specifically Lumicrease Grey 3 LBN and Superlite OrangeLLLWF) and 1% of previously dissolved 1:2 metal-complex dyestuffs (i.e.Irgalan Grey BL Capracyl Yellow NW), these percentages being based onthe weight of the fabric.

The dyeing was run for 10 minutes at 100 F. and then 10% (on the weightof the cloth) of previously dissolved sodium chloride was added and thedyeing run for an additional 10 minutes at 100 F. The sodium chloridewas used for the purpose of increasing the exhaustion rate of the directdyes. Only 10% thereof was used to prevent excessive decharging of thenylon surface.

The dyebath was heated to 200 F. in one hour and dyeing was continued at200 F. for an additional hour after which the fabric was rinsed well,dried and finished.

The above procedure was carried out on two separate dyeings of fouryards each and compared to conventional dyeings using the same fabricand shade. The degree of contrast achieved between the nylon 6 and nylon66 was much greater using the present process than was the case with theconventional dyeing. In other dyeings of nylon "piece fabric, it wasalso apparent that the present process could be used to reduce barreeffect.

Example II y ating from the scope thereof as set forth in the followingclaims wherein I claim: 7

1. In a process for dyeing textile materials containing fibers of afirst nylon characterized by the general formula and containing fibersof a second nylon characterized by the general formula 1: representing awhole number in both instances, the improvement which comprises dyeingsaid materials in an essentially neutral dyebath which containspolyvinylpyn' rolidone and ethoxylated tallow alcohol.

2. In a process for dyeing textile materials containing fibers of afirst nylon characterized by the general formula and containing fibersof a second nylon characterized by the general formula V NH [CONH(CHCONH- (CH ,,--COOH n representing a whole number in both instances, theimprovement which comprises dyeing said materials in an essentiallyneutral aqueous dyebath containing a nylon dyestuff, a water-solubleagent which has a greater affinity for said dyestuff than for nylon andforms a complex therewith thereby preventing the dyestuif from bind ingwith nylon through the amino group therein; and a dispersing agent forsaid complex which builds in solution a large micelle structure. 0

I 3. In a process for dyeing textile materials containing fibers of afirst nylon characterized by the general formula and containing fibersof a second nylon-characterized by I the general formula V Nl-I [CONH(CH-CONH(CH COOH sisting of ethoxylated tallow alcohol and a partiallysulfonated long chain saturated fatty acid. 7 4. The process of claim 3wherein the amount of said complex-forming member is from 0.5% to 1%,and the amount of said dispersing agent is from 0.5% to 2%, saidpercentages being based on the weight of material being dyed.

5. The process of claim 4 wherein the water content of said dyebath issuch as to provide about a 20 to 1 ratio between the water therein andthe material being dyed.

6. The process of claim 5 wherein the dyestufi is a 1:2 metal-complexdye.

References Cited in the file of this patent UNITED STATES PATENTS2,888,313 Mautner May 26, 1959 2,952,506 Dellis Sept. 13, 1960 53,025,127 Iannarone Mar. 13, 1962 FOREIGN PATENTS 524,317 Belgium Mar.16, 1956 OTHER REFERENCES

1. IN A PROCESS FOR DYEING TEXTILE MATERIALS CONTAINING FIBERS OF AFIRST NYLON CHARACTERIZED BY THE GENERAL FORMULA